Anhydrous (or dehydrated) dicalcium phosphate has been commonly used as an excipient for tableting, a source of calcium and phosphorus in nutritional supplements, a polishing agent within dentifrices, a carrier for human and animal nutrients, as well as a dough conditioner for yeast-containing foodstuffs. For tableting and nutrition applications, such anhydrous dicalcium phosphate materials should be able to compress directly and easily and simultaneous exhibit good flow character. Powdered materials of such materials tend to exhibit cementation and thus cannot easily flow (without excessive amounts of required energy and thus increased processing costs), nor can produce a stable compressed tablet.
It has been a combined aim for such materials to deliver the highest level of available calcium within a form that permits proper transfer, tablet production, and ultimate ingestion by a target patient. As such, the provision of granulated dicalcium phosphate has been a requirement within the subject industries. Without granulation, the subject dicalcium phosphate materials would exhibit, as a powder, poor flowability characteristics, cementation during storage and high levels of dusting when transferred, at least, while incorporating such materials into proper orally ingested tablets and/or capsules. Thus, there is a need to provide cost-effective granulation of such materials to meet the requirements noted above.
Granulation has typically included the utilization of binder systems to facilitate the massing of dicalcium phosphate powders into larger particle size granules. Such a method, although well known, and extensively followed, exhibits certain drawbacks that leave room for improvement. For instance, such binders, including, without limitation, starch, gelatin, hydroxypropyl methylcellulose, polyvinylpyrrolidone, and the like, are relatively expensive and/or require relatively high levels of use to effectively provide the needed degree of granulation to occur. In fact, a level of 5.0 parts per hundred parts of dicalcium phosphate is generally the low level of binder additive present within final granulated dicalcium phosphate formulations. This produces a material that exhibits at most 95% bioavailable dicalcium phosphate for utilization by the target patient/user within a typical tablet/capsule, or requires the production of relatively large size tablets and/or capsules to increase the amount of bioavailable dicalcium phosphate present therein. An increase in the amount of bioavailable dicalcium phosphate would thus be a desired result in order to reduce binder costs, reduce the amount of additives needed to permit granulation, and reduce pill sizes without restricting or reducing the amount of calcium available to the patient/user during ingestion. All of these benefits would necessarily result without any concomitant loss in flowability of the granulated dicalcium phosphate in comparison with the typical binder-granulated types as well. To date, although such granulated dicalcium phosphate is well known and used widely, particularly within the nutrition and pharmaceutical industries, as noted above, such a desirable improvement has not been achieved.
In the past, the typical manner of producing anhydrous dicalcium phosphate involved the initial precipitation of either anhydrous (dehydrated) or dihydrated dicalcium phosphate by introducing lime or calcium carbonate into a vessel of diluted phosphoric acid, followed by the separation via filtration of the resultant precipitated solid from the mixture, drying the resultant particles, and then subsequent granulation of the collected fine particles. Subsequently, if the dihydrate was formed, thorough drying was necessary to drive of the water to provide the ultimate dehydrated form. Such an involved method was not only cumbersome to perform, but required multiple steps that resulted in increased manufacturing costs, and involved large amounts of potential dangerous phosphoric acid. A less involved, and thus, presumably, less costly alternative is thus highly desired within the industry. To date, no method of directly producing granulated dehydrated dicalcium phosphate that involves a less labor intensive process than that described above has been provided within the pertinent industry.